I used to carry my SLR and laptop with me in my huge backpack every day, but a few changes have resulted in almost never bringing my camera day-to-day anymore:

My commute is now on the subway, which is much more crowded and much less practical for backpack-wearing. I have a great messenger bag that works much better for the subway, but it can’t comfortably hold more than a few pounds. (Heavy messenger bags are awful for your lower back.)

I never need to bring a laptop to work anymore, as I have a desktop there, and I can no longer use a laptop during the commute.

It’s often easiest not to bring a bag at all, especially when wearing a jacket.

Through lens and body upgrades, my SLR gear has grown larger and heavier. I love having it when I want to take high-quality photos, but I’ve missed a lot of shots because I didn’t have my insanely great camera with me.

I’ve started considering getting a second, inexpensive camera that’s small and light enough that I could keep it in a jacket pocket or a small bag without much of a weight cost.

Compact cameras and I don’t usually get along because we have very different priorities: I like optical and technical perfection with available manual controls, and don’t care much for most consumer-oriented features (like face detection, lots of “scene” modes, huge zoom ranges at the expense of optical quality, and insanely high pixel densities at the expense of noise). Compact cameras are almost always designed for the opposite type of consumer that I am because there are a lot more of them.

Compact cameras targeted at people like me do exist: Gruber’s favorites, the Ricoh GR Digital series, are great examples. But they’re limited, expensive, and rare.

Then there’s the iPhone dilemma: I already have an iPhone 3GS, which contains a passable camera for many situations. It’s a huge improvement over the fixed-focus iPhone 3G camera, but it’s nowhere near the optical quality and versatility of a lens and sensor larger than the tip of a ballpoint pen. But it’s always with me, always charged, and much more versatile in software and on-the-go actions. It’s therefore much more difficult to justify a standalone compact camera to sit between the iPhone and the 5D Mark II, especially since most of them wouldn’t satisfy my needs very well anyway.